A collection which forwards all its method calls to another collection.
Subclasses should override one or more methods to modify the behavior of the
backing collection as desired per the decorator pattern.

Warning: The methods of ForwardingCollection forward
indiscriminately to the methods of the delegate. For example,
overriding add(java.lang.Object) alone will not change the behavior of addAll(java.util.Collection), which can lead to unexpected behavior. In this case, you should
override addAll as well, either providing your own implementation, or
delegating to the provided standardAddAll method.

The standard methods are not guaranteed to be thread-safe, even
when all of the methods that they depend on are thread-safe.

A sensible definition of isEmpty() as !iterator().hasNext.
If you override isEmpty(), you may wish to override isEmpty()
to forward to this implementation. Alternately, it may be more efficient to
implement isEmpty as size() == 0.